It’s easy to import and export feed sources since they are stored as custom post types in WordPress. The process is, therefore, the same as if you were to import/export posts or pages. This can be seen in the video below, starting at the 53 second mark.
Importing Feed Sources
Navigate to WordPress admin > Tools > Import, and choose the WordPress Importer. If you haven’t installed it yet, you will be prompted to do so.
On the Import page, choose the file that you want to upload and import by using Choose File, and then clicking Upload File and Import.
Exporting Feed Sources
To export your feed sources to a file, navigate to WordPress admin > Tools > Export, choose Feed Sources and click the Download Export File button.
If you wish to export your Feed Items or your Blacklist, you can do so by using this same method, but choosing Feed Items or Blacklist in the Export page. They can then be imported later in the same way Feed Sources are imported.